ALS9Q - Section 9 The s-Block Elements 1 SKH Bishop Baker...

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Section 9/ The s-Block Elements / SKH Bishop Baker Secondary School AL Chemistry Section 9 The s-Block Elements 81 IIB Q.7 (a) The hydration energies of the alkali metal-ions in kJ mol - 1 are as follows : Li + Na + K + Rb + Ca 2+ 499 390 305 281 248 Give an explanation for the trend in these figures. (4 marks) (b) The hydrated ion Be(H 2 O) 4 2+ acts as an acid in water. Suggest an explanation. (4 marks) 83 IA Q.4 (b) What is observed when sodium is burnt in air ? Name the products of the combustion. (2 marks) 83 IIB Q.8 Magnesium, calcium, strontium and barium are elements in Group II of the Periodic Table. By reference to the information given in the table below, or otherwise, answer the following questions which relate to strontium : Flame test Abundance of compounds Solubility of in ores in seawater chloride sulphate Magnesium yes yes soluble soluble Calcium red colour yes no soluble sparingly soluble Barium green colour no no soluble insoluble (a) (i) What is the flame colour of strontium ? (ii) Describe the steps involved in carrying out a flame test. (4 marks) (b) Predict the abundance of strontium compounds compared with the other Group II elements, giving reasons. Suggest the most abundant ore of strontium and give its formula. (4 marks) (c) (i) Why is it not practicable economically to extract strontium from seawater ? (ii) Describe how strontium maybe extracted from a suitable raw material. (4 marks) (d) Give an explanation for any trends in the solubility of Group II sulphates. Describe a chemical test to confirm the presence of strontium ions in the presence of calcium ions. (8 marks) 85 IA Q.2 (c) Potassium forms three oxides. (i) Write the formula for each oxide. (ii) Give a balanced equation for the reaction of each one with cold water. (5 marks) 1
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Section 9/ The s-Block Elements / 86 IA Q.2 (b) Using ‘dot and cross’ diagrams, show the bonding involved in the three species : O 2 , O 2 2 - , O 2 - .
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